Growth Changes and Sexual Dimorphism in the Stomiatoid Fish Echiostoma barbatum

Meristic and morphometric characters of a large collection of Echiostoma barbatum Lowe from off the Mississippi Delta were analyzed with particular respect to allometric growth and sexual dimorphism. As standard length increases, length of the barbel and dimensions of its two bulbs become reduced in actual and relative size, while the stem filaments increase in number and decrease in length. In large males, the postocular organ is longer than in large females and lacks the posterior narrowing seen in females. Females appear to mature at a larger size and to reach a larger maximum size than males. Among 100 specimens, females outnumber males 2: 1, the imbalance caused by the predominance of large females. There is only one known species of Echiostoma. All other nominal species in this genus are synonyms of E. barbatum.